The present invention relates to hydraulic machines in general, and more particularly to improvements in gear type hydraulic machines which can be operated as pumps or motors.
It is known to mount the stubs of mating gears of a hydraulic pump or motor in annular bearing members which are non-rotatably installed in the housing of the machine. It is also known to establish in the bearing members hydrostatic pressure fields to counteract the forces which are stubs transmit radially of the respective bearing members.
In a presently known gear type hydraulic machine, the stubs of the mating gears are mounted in two eight-shaped bearing members each of which has two bores, one for a stub of the first gear and the other for a stub of the other gear. The surfaces surrounding the bores of the eight-shaped bearing members have recesses which are to be filled with pressurized fluid to thus establish hydrostatic pressure fields in the region where a stub tends to bear directly against the internal surface of the respective bearing member. such machines have met with little success because the hydrostatic pressure fields are incapable of compensating for all or the major part of forces which the stubs apply to the bearing members and also because the pressure fields cannot invariably prevent metal-to-metal contact between the stubs and the respective bearing members. The situation is aggravated when the axis of a stub does not coincide with the axis of the respective bore; this invariably causes substantial variations in the magnitude of forces acting on the bearing members as considered in the axial direction of the stubs. Such unequal distribution of pressures results in pronounced flattening of internal surfaces of the bearing members as well as in excessive wear upon those end faces of the bearing members which are adjacent to the respective end faces of the gears. This contributes to more pronounced leakage of fluid and reduces the efficiency of the machine.